Laser processing of materials has exhibited enormous growth since the commercial availability of the excimer laser in the late 1970s. Materials processing has been investigated in the realm of organic polymers, ceramics, metals and semiconductors. Semiconductor processing of silicon for VLSI applications range from laser-assisted etching, as disclosed in S. D. Russell et al's. "Excimer Laser-Assisted Etching of Silicon Using Chloropentafluoroethane," in R. Rosenberg et al., eds., In-Situ Patterning: Selective Area Deposition and Etching, Mater. Res. Soc. Proc., vol. 158 (1990), p. 325; chemical vapor deposition (CVD), in the article "Laser-Induced Plasmas for Primary Ion Deposition of Epitaxial Ge and Si Films by D. Lubben et al., J. Vac. Sci. Technol. B, Vol. 3 (1985), p. 968; and alloy formation, see J. R. Abelson et al., "Epitaxial Ge.sub.x Si.sub.1-x /Si (100) Structures Produced by Pulsed Laser Mixing of Evaporated Ge on Si (100) Substrates", Appl. Phys. Lett., vol. 52 (1988), p. 230; to name a few. Laser activation of ion implanted dopant has long been known as an alternative to conventional furnace annealing, as discussed in A. E. Bell's "Review and Analysis of Laser Annealing," RCA Review, vol. 40 (1979), p. 295; and L. D. Hess et al.'s "Applications of Laser Annealing in IC Fabrication", in J. Narayan et al., eds., Laser-Solid Interactions and Transient Thermal Processing of Materials, Mat. Res. Soc. Symp. Proc., vol. 13 (1983), p. 337. Techniques such as Gas Immersion Laser Doping (GILD) have proven valuable in the formation of shallow junctions in bulk silicon; refer to R. J. Pressley's, "Gas Immersion Laser Diffusion (GILDing)", in C. C. Tang, ed., Laser Processing of Semiconductor Devices, Proc. SPIE, vol. 385 (1983), p. 30. In addition, examination of excimer laser annealing of implant damage in bulk silicon has been demonstrated in D. H. Lowndes et al.'s "Pulsed Excimer Laser (308 nm) Annealing of Ion Implanted Silicon and Solar Cell Fabrication" and disclosed in J. Narayan et al., eds., Laser-Solid Interactions and Transient Thermal Processing of Materials, Mat. Res. Soc. Symp. Proc., vol. 13 (1983), p. 407. Excimer lasers recently have been used in the fabrication of complex devices such as the bipolar transistors applications, see K. H. Weiner et al.'s "Thin-Base Bipolar Transistor Fabrication Using Gas Immersion Laser Doping", IEEE Electron Dev. Lett., vol. 10 (1989), p. 260; and S. D. Russell et al.'s, "Bipolar Transistors in Silicon-On-Sapphire (SOS): Effects of Nanosecond Thermal Processing", in IEEE SOS/SOI Technology Conference Proceedings (1990). Excimer lasers also recently have been used in the fabrication of backside illuminated CCDs as described in the pending patent applications referred to above.
Processing of semiconductor compounds often involves the use of toxic, corrosive, flammable, and pyroforic gases. This adds enormous constraints on the processing techniques and sample handling involved in order to provide equipment and operator safety. Laser processing complicates these issues by the requirement of a contained processing environment to meet OSHA regulations for class IV lasers. The prior art in microelectronics laser processing has met these requirements using complex systems which can introduce a variety of gases into a processing chamber at a predetermined pressure, with subsequent evacuation of the effluent. Such a system is described in detail in the pending patent application of S. D. Russell et al.'s "Excimer Laser-Assisted Etching of Silicon Using Halocarbon Ambients", U.S. Ser. No. 07/501,707. However, this typical research type vessel is inappropriate for high volume production sample handling. Similar complex chambers have been reported by S. Palmer et al. in "Laser-Induced Etching of Silicon at 248 nm by F.sub.2 /Ne," Conference on Lasers and Electro-Optics Technical Digest Series 1988, vol. 7 (Optical Society of America, Washington, D.C., 1988), p. 284. In addition to inefficient sample exchange, handling of microelectronic die that are highly susceptible to mechanical damage, such as backside illuminated CCDs which have thin membranes, about 10 microns in thickness, and devices which are sensitive to electrostatic discharge (ESD) damage, cannot be readily handled with these designs, even in low volume research environments.
Alternative techniques have been used for laser processing in applications that do not require the use of dangerous gases. Two examples are laser activation of ion implanted dopant and laser ablation of polymers. The procedure used for the former process involves the use of a single wafer holder, which is evacuated to a base pressure (nominally 20 millitorr) and backfilled to atmospheric pressure in an inert ambient such as argon. Ablation of polymers may take place in air; therefore, exhaust schemes are used to remove particulates from the sample being processed. One technique has been marketed by Image Micro Systems. The complexities in imaging an excimer laser to a small uniform spot for ablation applications requires careful integration of the optics, sample positioning, and exhaust system. Such a commercially available system utilizes a microscope stage for micropositioning of the sample, but is not designed for rapid sample exchange or handling. Wafer handling prevalent in the semiconductor industry has been incorporated into some systems, for example, the excimer laser planarization system by XMR. In the above systems, generally, single sample handling is involved and there are no obvious modifications for handling mechanically and/or electrostatically fragile die for laser processing. Schemes using complex optical recognition with robotic pick-and-place methods would still be difficult with the mechanical and ESD constraints
Thus, it is evident that advances in laser processing has moved this technique into the realm of a production tool and the need is apparent for novel sample handling techniques which can combine rapid sample handling with the optical, mechanical and gas handling constraints unique to this technique. A need exists for a method of rapid sample handling in a production environment for laser processing of individual microelectronic die in an inert or nontoxic/non-corrosive ambient which is particularly suited for handling partially fabricated die, and die which are susceptible to mechanical and electrostatic damage. It is particularly applicable for backside illuminated CCDs requiring backside dopant activation and laser texturing of sidewalls as described in the above referenced pending patents.